Substrate with Topological Features for Steering Fluidic Assembly LED Disks

ABSTRACT

Embodiments are related to integrated circuit (IC) fabrication and, more particularly, to a fluidic assembly process for the placement of light emitting diodes on a direct-emission display substrate.

RELATED APPLICATIONS

This application is a continuation of an application entitled “SUBSTRATEWITH TOPOLOGICAL FEATURES FOR STEERING FLUIDIC ASSEMBLY LED DISKSFLUIDICASSEMBLY TOP-CONTACT LED DISK”, invented by Mark Albert Crowder et al.,U.S. patent application Ser. No. 15/682260, filed Aug. 21, 2017; whichis a continuation of U.S. Pat. No. 9,955,310 “SUBSTRATE WITH TOPOLOGICALFEATURES FOR STEERING FLUIDIC ASSEMBLY LED DISKSFLUIDIC ASSEMBLYTOP-CONTACT LED DISK”, invented by Mark Albert Crowder et al., filedJul. 27, 2016 and issued Sep. 5, 2017. The entirety of both of theaforementioned application is incorporated herein for all purposes.

FIELD OF THE INVENTION

Embodiments are related to integrated circuit (IC) fabrication and, moreparticularly, to a fluidic assembly process for the placement of lightemitting diodes on a direct-emission display substrate.

BACKGROUND

LED displays, LED display components, and arrayed LED devices include alarge number of diodes formed or placed at defined locations across thesurface of the display or device. Fluidic assembly may be used forassembling diodes in relation to a substrate for use in manufacturingLED devices. Such assembly is often a stochastic process whereby LEDdevices are deposited into wells on a substrate. By its nature, such astochastic process is unpredictable leading to uncontrollable assembly.

Hence, for at least the aforementioned reasons, there exists a need inthe art for advanced systems and methods for manufacturing LED displays,LED display components, and LED devices.

SUMMARY

Embodiments are related to integrated circuit (IC) fabrication and, moreparticularly, to a fluidic assembly process for the placement of lightemitting diodes on a direct-emission display substrate.

This summary provides only a general outline of some embodiments of theinvention. The phrases “in one embodiment,” “according to oneembodiment,” “in various embodiments”, “in one or more embodiments”, “inparticular embodiments” and the like generally mean the particularfeature, structure, or characteristic following the phrase is includedin at least one embodiment of the present invention, and may be includedin more than one embodiment of the present invention. Importantly, suchphrases do not necessarily refer to the same embodiment. Many otherembodiments of the invention will become more fully apparent from thefollowing detailed description, the appended claims and the accompanyingdrawings.

BRIEF DESCRIPTION OF THE FIGURES

A further understanding of the various embodiments of the presentinvention may be realized by reference to the figures which aredescribed in remaining portions of the specification. In the figures,like reference numerals are used throughout several figures to refer tosimilar components. In some instances, a sub-label consisting of a lowercase letter is associated with a reference numeral to denote one ofmultiple similar components. When reference is made to a referencenumeral without specification to an existing sub-label, it is intendedto refer to all such multiple similar components.

FIG. 1 depicts a fluidic assembly system capable of moving a suspensioncomposed of a carrier liquid and a plurality of diode objects relativeto the surface of a substrate including in accordance with one or moreembodiments of the present inventions;

FIGS. 2a-2c show a portion of a panel including wells into which diodeobjects are deposited and steering structures in accordance with variousembodiments of the present inventions;

FIGS. 3a-3b show a portion of a panel including wells into which diodeobjects are deposited and off-center steering structures in accordancewith some embodiments of the present inventions;

FIGS. 4a-4b show a portion of yet another panel including wells intowhich diode objects are deposited where each of the wells includes athrough-hole via, and steering structures in accordance with variousembodiments of the present inventions;

FIG. 5 is a flow diagram depicting a method in accordance with one ormore embodiments of the present inventions for assembling diode objectsinto a panel; and

FIGS. 6a-6g show a series of processes for assembling diode objects intoa panel in accordance with one or more embodiments of the presentinventions.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

Embodiments are related to integrated circuit (IC) fabrication and, moreparticularly, to a fluidic assembly process for the placement of lightemitting diodes on a direct-emission display substrate.

Some embodiments provide fluidic assembly direct-emission display panelsthat include: a substrate, a first film, and a second film. Thesubstrate includes a planar top surface and interconnect pads aligned ina plurality of rows. The first film is disposed over the top surface ofthe substrate and includes a plurality of wells, where each of theplurality of wells expose corresponding ones of the interconnect pads.The second film is disposed over the first film, wherein the second filmincludes at least one steering feature surrounding two or more of theplurality of wells.

In some instances of the aforementioned embodiments, the steeringfeature is a slot with a cross-section greater than an opening of eachof the two or more of the plurality of wells. In some such instances,the two or more of the plurality of wells is part of a column of wells.In various instances of the aforementioned embodiments, the second filmis a removable material. In one or more instances of the aforementionedembodiments, the two or more of the plurality of wells each have aperimeter. The steering feature in the second film has a sidewall havingthrough-indentations coextensive with at least a portion of theperimeter of each of the two or more of the plurality of wells. Invarious instances of the aforementioned embodiments, the substratefurther includes a plurality of bottom electrically conductive traces,with each bottom conductive trace associated with a corresponding one ofthe plurality of rows.

In various instances of the aforementioned embodiments, the substratefurther includes a plurality of bottom electrically conductive traces,with each bottom electrically conductive trace being associated with acorresponding one of the plurality of rows. In some such instances, alight emitting diode (LED) disk is situated in each of the two or moreof the plurality of wells. The LED disk has a cross-sectional width lessthan a cross-sectional opening of each of the two or more of theplurality of wells, and a bottom surface with a lower contact to make anelectrical connection with one of the interconnect pads. In some cases,the first film has a thickness and the LED disks have about the samethickness. The panel further includes: an insulator material fillingeach steering feature, with vias exposing a top contact of each of theLED disks; and a plurality of top electrically conductive traces, witheach top conductive trace connected to a top contact of each of the LEDdisks in a corresponding column of wells.

In one or more instances of the aforementioned embodiments, thesubstrate includes a through-hole via (THV) co-located with each of theinterconnect pads. In some cases, the substrate includes a through-holevia (THV) co-located with each of the interconnect pads, and across-sectional opening of the THV is less than a width of each of theLED disks.

Other embodiments provide methods for forming a fluidic assemblydirect-emission display panel. The methods include: providing asubstrate with a planar top surface and interconnect pads aligned in aplurality of parallel rows; forming a first film overlying the substratetop surface; forming a plurality of wells in the first film, each wellhaving a cross-sectional opening, and aligned in a corresponding row andcolumn, exposing a corresponding interconnect pad; forming a second filmoverlying the first film; and forming a plurality of parallel slots inthe second film, where each slot has a width greater than the wellcross-sectional opening, exposing a corresponding column of wells.

In some instances of the aforementioned embodiments, forming the wellsin the first film includes forming wells with a perimeter; and formingthe slots in the second film includes forming through-indentations in asidewall of each slot, with the through-indentations exposing at least aportion of each well perimeter. In various instances of theaforementioned embodiments, the methods further include: flowing asuspension comprising a carrier fluid and a plurality of light emittingdiode (LED) disks, where each LED disk has a disk diameter less than thewell cross-sectional opening, and a bottom surface with a lower contact;channeling the ink into the plurality of slots; capturing the LED disksin the wells; and making contact between the lower contact of each LEDdisk and a corresponding bottom trace.

In one or more instances of the aforementioned embodiments, forming thefirst film includes forming the first film with a first thickness; whereflowing the suspension includes flowing a suspension including LED diskshaving about the first thickness. In such instances, the methods furtherinclude: subsequent to capturing the LED disks in the wells, forming aninsulating material to isolate LED disk sidewalls from subsequentlyformed top conductive traces, with vias exposing LED disk top contacts;and forming a plurality of top electrically conductive traces overlyingthe insulator material and connected the top contact of a column of LEDdisks. In particular instances of the aforementioned embodiments, themethods further include removing the second film subsequent to capturingthe LED disks in the wells. In one or more instances of theaforementioned embodiments, the methods further include formingthrough-hole vias (THVs) co-located with each interconnect pad prior toforming the first film.

In various instances of the aforementioned embodiments, the methodsfurther include: forming through-hole vias (THVs) co-located with eachinterconnect pad, each THV having a THV diameter less than the LED diskdiameter prior to forming the first film; and simultaneous with flowingthe ink, creating vacuum pressure through the THVs. In such instances,capturing the LED disks in the wells includes capturing the LED disks atleast partially in response to the vacuum pressure

Turning to FIG. 1, a fluidic assembly system 100 is shown that iscapable of moving a suspension 110 composed of a carrier liquid 115 anda plurality of diode objects 130 relative to the surface of a substrate140 including wells 142 in accordance with one or more embodiments ofthe present inventions. In some cases, the depth of wells 142 issubstantially equal to the height of diode objects 130, and the inletopening of wells 142 is greater that the width of diode objects 130 suchthat only one diode object 130 deposits into any given well 142. Itshould be noted that while embodiments discuss depositing diode objects130 into wells 142, that other devices or objects may be deposited inaccordance with different embodiments of the present inventions.

A depositing device 150 deposits suspension 110 over the surface ofsubstrate 140 with suspension 110 held on top of substrate 140 by sides120 of a dam structure. In some embodiments, depositing device 150 is apump with access to a reservoir of suspension 110. A suspension movementdevice 160 agitates suspension 110 deposited on substrate 140 such thatdiode objects 130 move relative to the surface of substrate 140. Asdiode objects 130 move relative to the surface of substrate 140 theydeposit into wells 142 in either a non-inverted orientation or aninverted orientation. In some embodiments, suspension movement device160 is a brush that moves in three dimensions. Based upon the disclosureprovided herein, one of ordinary skill in the art will recognize avariety of devices that may be used to perform the function ofsuspension movement device 160 including, but not limited to, a pump.

A capture device 170 includes an inlet extending into suspension 110 andcapable of recovering a portion of suspension 110 including a portion ofcarrier liquid 115 and non-deposited diode objects 130, and returningthe recovered material for reuse. In some embodiments, capture device170 is a pump. In some cases, substrate 140 may be implemented similarto one of the substrates discussed below in relation to FIGS. 2-5.Further, in some cases, substrate 140 may be formed using one or moreprocesses discussed below in relation to FIGS. 6-7.

Turning to FIGS. 2a -2 b, a cross-sectional view 200 and a top view 201of a portion of a panel including wells 212 into which diode objects 226(e.g., Light Emitting Diodes) are deposited and steering structures 220is shown in accordance with various embodiments of the presentinventions. As shown, the panel includes a substrate 202 with a planartop surface 204 and interconnect pads 206 aligned in a plurality ofrows. Substrate 202 may be a transparent material such as glass, quartz,or a plastic. While FIGS. 2a-2b show only two columns and two rowsincorporating four wells 212, a number of rows (indicated by the smallcase letter following the element identifying numbers (e.g., 220 a,where the “a” indicates the row)) and columns (indicated by the dashnumber following the element identifying numbers (e.g., 240-1, where the“1” indicates the column)) can be used to form a panel. In someembodiments, a thickness of substrate 202 measured form a bottom surfaceto top surface 204 is three hundred (300) microns. Based upon thedisclosure provided herein, one of ordinary skill in the art willappreciate other thicknesses that may be used for substrate 202 inaccordance with different embodiments.

A first film 210 is disposed over top surface 204 of substrate 202, andwells 212 are defined in first film 210. Being disposed over may includebeing formed directly on substrate 202 or atop one or more layers whichthemselves overly substrate 202. Each well 212 is aligned in acorresponding row (again, indicated by the small case letter followingthe element identifying numbers) and column (again, indicated by thedash number following the element identifying numbers). Each well 212has a cross-sectional opening 216 that exposes a correspondinginterconnect pad 206. As one particular example, well 212 a-1 exposesinterconnected pad 206 a. In this embodiment, cross-sectional opening216 is depicted as circular, but alternatively it may be square,rectangular, oval, or have a counterbore pocket structure. Such acounterbore pocket structure may be similar to that disclosed in U.S.patent application Ser. No. 14/530,230, entitled “ COUNTERBORE POCKETSTRUCTURE FOR FLUIDIC ASSEMBLY”, and filed Oct. 31, 2014. The entiretyof the aforementioned reference is incorporated herein by reference forall purposes. First film 210 may be formed using any process known inthe art for forming a layer with wells. As just one example, first film210 may be formed using a conformal deposition and selective etchingprocess. Based upon the disclosure provided herein, one of ordinaryskill in the art will recognize a variety of processes that may be usedto form first film 210 in accordance with different embodiments. In someembodiments, wells 212 are set off from each other by five hundred (500)microns (i.e., 10⁻⁶ m) (i.e., from a center of one well to the center ofthe next well in both the X and Y directions). Based upon the disclosureprovided herein, one of ordinary skill in the art will appreciate otherdistances at which wells 212 may be offset from one another inaccordance with different embodiments. In some embodiments,cross-sectional opening 216 of wells 212 is sixty (60) microns. Basedupon the disclosure provided herein, one of ordinary skill in the artwill appreciate other cross-sectional widths that may be used for wells212 in accordance with different embodiments.

A second film 218 is disposed over first film 210. Being disposed overmay include being formed directly on first film 210 or atop one or morelayers which themselves overly first film 210. Second film 218 includesplurality of parallel steering structures 220. Each steering structure220 has a width 222 that is greater than cross-sectional opening 216 ofwells 212 and surrounds a number of wells (e.g., steering structure 220a surrounds wells 212 a-1 and 212 a-2; and steering structure 220 bsurrounds wells 212 b-1 and 212 b-2) such that the surrounded wells areexposed within the respective steering structure 220. In someembodiments, cross-sectional opening 222 of steering structures 220 isbetween seventy-five (75) and one hundred fifty (150) microns. Basedupon the disclosure provided herein, one of ordinary skill in the artwill appreciate other cross-sectional widths that may be used forsteering structures 220 in accordance with different embodiments. Invarious embodiments, the depth of steering structures measured form thebottom of wells 212 is between five hundred (500) and seven hundred(700) microns. Based upon the disclosure provided herein, one ofordinary skill in the art will appreciate other depths that may be usedfor steering structures 220 in accordance with different embodiments.

In some embodiments, second film 218 is a removable material that can beremoved prior to deploying the final assembled panel. In otherembodiments, second film 218 is not removed prior to deploying the finalassembled panel. In some embodiments, second film 218 is a differentmaterial than that of first film 210. In other embodiments, second film218 is the same material as that of first film 210. An example materialfor second film 218 is a positive photoresist, as this would permitphotolithographic patterning and fluidic assembly with a water orisopropanol suspension, and it can be rinsed away after the process withacetone or ethyl lactate, neither of which would affect the polyimidelaminate. In this embodiment, wells 212 are approximately centeredwithin their respective steering structure 220 (i.e., wells 212 arelocated approximately equal distant from each wall of their respectivesteering structure 220). However, as described in other examples below,that condition is not a necessity. Second film 218 may be formed usingany process known in the art for forming a layer with steeringstructures. As one example, second film 218 may be formed by applyingthe material of second film 218, and lithographically patterning andetching to form steering structures 220 aligned to wells 212. Based uponthe disclosure provided herein, one of ordinary skill in the art willrecognize a variety of processes that may be used to form second film218 in accordance with different embodiments.

Diode objects 226 are deposited into wells such that a bottom contact oneach of diode objects are electrically connected to interconnect pads206 exposed by wells 212. A plurality of top electrically conductivetraces 240 are disposed over a column of wells 212 such that anelectrical connection at a top contact 238 of each of the diode objects226 within a given column is made. An insulator material 234 is formedaround each of the diode objects 226 within their respective well 212.As would be known in the art, diode objects 226 may include a lowermaterial with either a p-dopant or an n-dopant and an upper material ofthe opposite dopant type, with an intervening multiple quantum well(MQW). The MQW may be a series of quantum well shells (typically 5layers—e.g., alternating 5 nanometer (nm) of indium gallium nitride(InGaN) with 9 nm of n-doped GaN (n-GaN)). There may also be an aluminumgallium nitride (AlGaN) electron blocking layer between MQW layers andthe p-doped disk. The outer shell may be p-doped GaN (Mg doping) about200 nm thick. A high-brightness blue LED can be formed, or a green LEDif a higher indium content is used in the MQW. The lower material may bea material such as p-GaN, p-doped aluminum gallium indium phosphide(p-AlGaInP), n-GaN, or n-AlGaInP. The upper material may be the same asthe lower material, but oppositely doped. It should be noted that theaforementioned discussion of materials and structure of diode objects226 is not exhaustive, and that one of ordinary skill in the art willrecognize other materials and structures that may be used in relation todifferent embodiments.

In some embodiments, first film 210 has a thickness 232 and diodeobjects 226 exhibit a similar thickness. In some cases, the differencebetween the thickness of diode object 226 and thickness 232 is less thanfifty (50) percent of the overall thickness of diode object 226. In someembodiments, thickness 232 is five (5) microns. Based upon thedisclosure provided herein, one of ordinary skill in the art willappreciate other thicknesses that may be used for first film 210 inaccordance with different embodiments.

Turning to FIG. 2c , a top view 203 of a larger portion of the panel ofFIGS. 2a-2b is depicted that includes more rows (i.e., “1” through “5”)and columns (i.e., “a” through “f”) than previously shown. It should benoted that panels in accordance with different embodiments may include amuch larger number of rows and columns than what is depicted in FIG. 2c. As shown, substrate 202 further supports a plurality of bottomelectrically conductive traces 224, with each bottom conductive traceassociated with a corresponding row of wells 212 and interconnect pads206. As a particular example, a bottom electrically conductive trace 224a is associated with a row “a” including wells 212 a-1, 212 a-2, 212a-3, 212 a-4, 212 a-5. Steering structures 220 encompass wells 212 (andthus, interconnect pads 206 exposed by the wells) in each row. As aparticular example, in the “c” row, steering structure 220 c encompasseswells 212 c-1, 212 c-2, 212 c-3, 212 c-4, 212 c-5 (and the correspondinginterconnect pads 206 exposed by the wells). Bottom electricallyconductive traces 224 electrically connect interconnect pads 206 withina given row. Like interconnect pads 206, bottom electrically conductivetraces 224 are disposed over substrate 202 and below first film 210.Interconnect pads 206 and bottom electrically conductive traces 224 maybe formed using any process known in the art for forming an electricalcontact layer. As just one example, interconnect pads 206 and bottomelectrically conductive traces 224 may be formed using a conformaldeposition and selective etching process. Based upon the disclosureprovided herein, one of ordinary skill in the art will recognize avariety of processes that may be used to form interconnect pads 206 andbottom electrically conductive traces 224 in accordance with differentembodiments.

In one aspect not shown, the wells are formed in the substrate, which istypically a glass or plastic material. In this aspect the second (i.e.,slot forming) layer is more easily removed after fluidic assembly. Inanother aspect not shown, slots may be formed from multiple removablelayers for steering disks during fluidic assembly, where the slots widthof an overlying film is greater than the slot width of an underlyingfilm.

Turning to FIGS. 3a -3 b, a cross-sectional view 300 and a top view 301of a portion of a panel including wells 312 into which diode objects 326(e.g., Light Emitting Diodes) are deposited and off-center steeringstructures 320 is shown in accordance with some embodiments of thepresent inventions. As shown, the panel includes a substrate 302 with aplanar top surface 304 and interconnect pads 306 aligned in a pluralityof rows. Substrate 302 may be a transparent material such as glass,quartz, or a plastic. While FIGS. 3a-3b show only two columns and tworows incorporating four wells 312, a number of rows (indicated by thesmall case letter following the element identifying numbers (e.g., 320a, where the “a” indicates the row)) and columns (indicated by the dashnumber following the element identifying numbers (e.g., 340-1, where the“1” indicates the column)) can be used to form a panel.

A first film 310 is disposed over top surface 304 of substrate 302, andwells 312 are defined in first film 310. Each well 312 is aligned in acorresponding row (again, indicated by the small case letter followingthe element identifying numbers) and column (again, indicated by thedash number following the element identifying numbers). Each well 312has a cross-sectional opening 316 that exposes a correspondinginterconnect pad 306. As one particular example, well 312 a-1 exposesinterconnected pad 306 a. In this embodiment, cross-sectional opening316 is depicted as circular, but alternatively it may be square,rectangular, oval, or have a counterbore pocket structure. First film310 may be formed using any process known in the art for forming a layerwith wells. As just one example, first film 310 may be formed using aconformal deposition and selective etching process. Based upon thedisclosure provided herein, one of ordinary skill in the art willrecognize a variety of processes that may be used to form first film 310in accordance with different embodiments.

A second film 318 is disposed over first film 310. Second film 318includes plurality of parallel steering structures 320. Each steeringstructure 320 has a width 322 that is greater than cross-sectionalopening 316 of wells 312 and surrounds a number of wells (e.g., steeringstructure 320 a surrounds wells 312 a-1 and 312 a-2; and steeringstructure 320 b surrounds wells 312 b-1 and 312 b-2) such that thesurrounded wells are exposed within the respective steering structure320. In some embodiments, second film 318 is a removable material thatcan be removed prior to deploying the final assembled panel. In otherembodiments, second film 318 is not removed prior to deploying the finalassembled panel. In some embodiments, second film 318 is a differentmaterial than that of first film 310. In other embodiments, second film318 is the same material as that of first film 310. In this embodiment,wells 312 off-center within steering structures 220 such that: a portionof the perimeters of wells 312 a-1 and 312 a-2 are coextensive with asidewall 390 of second film 318, but a sidewall 391 of second film 318is not coextensive with any portion of the perimeters of wells 312 a-1and 312 a-2; and a portion of the perimeters of wells 312 b-1 and 312b-2 are coextensive with a sidewall 392 of second film 318, but asidewall 393 of second film 318 is not coextensive with any portion ofthe perimeters of wells 312 b-1 and 312 b-2. As shown, one sidewall ofsteering structure 320 a (i.e., side wall 390) is coextensive withapproximately half of the perimeter of each of wells 312 a-1 and 312a-2, and one sidewall of steering structure 320 b (i.e., side wall 392)is coextensive with approximately half of the perimeter of each of wells312 b-1 and 312 b-2). In other embodiments, less than half of theperimeters of wells 312 are coextensive with one sidewall of steeringstructures 320. Second film 318 may be formed using any process known inthe art for forming a layer with steering structures. As just oneexample, second film 318 may be formed using a conformal deposition andselective etching process. Based upon the disclosure provided herein,one of ordinary skill in the art will recognize a variety of processesthat may be used to form second film 318 in accordance with differentembodiments.

Diode objects 326 are deposited into wells such that a bottom contact oneach of diode objects are electrically connected to interconnect pads306 exposed by wells 312. A plurality of top electrically conductivetraces 340 are disposed over a column of wells 312 such that anelectrical connection at a top contact 338 of each of the diode objects326 within a given column is made. An insulator material 334 is formedaround each of the diode objects 326 within their respective well 312.As would be known in the art, diode objects 326 may include a lowermaterial with either a p-dopant or an n-dopant and an upper material ofthe opposite dopant type, with an intervening multiple quantum well(MQW). The MQW may be a series of quantum well shells (typically 5layers—e.g., alternating 5 nanometer (nm) of indium gallium nitride(InGaN) with 9 nm of n-doped GaN (n-GaN)). There may also be an aluminumgallium nitride (AlGaN) electron blocking layer between MQW layers andthe p-doped disk. The outer shell may be p-doped GaN (Mg doping) about300 nm thick. A high-brightness blue LED can be formed, or a green LEDif a higher indium content is used in the MQW. The lower material may bea material such as p-GaN, p-doped aluminum gallium indium phosphide(p-AlGaInP), n-GaN, or n-AlGaInP. The upper material may be the same asthe lower material, but oppositely doped. It should be noted that theaforementioned discussion of materials and structure of diode objects326 is not exhaustive, and that one of ordinary skill in the art willrecognize other materials and structures that may be used in relation todifferent embodiments.

In some embodiments, first film 310 has a first thickness 332 and diodeobjects 326 exhibit a similar thickness. In some cases, the differencebetween the thickness of diode object 326 and thickness 332 is less thanfifty (50) percent of the overall thickness of diode object 326.

Turning to FIGS. 4a -4 b, a cross-sectional view 400 and a top view 401of a portion of a panel including wells 412 into which diode objects 426(e.g., Light Emitting Diodes) are deposited, through-hole vias 480extending through a substrate 402 from the bottom of each of wells 412,and off-center steering structures 420 is shown in accordance with someembodiments of the present inventions. It should be noted that whilewells 412 are shown off-center from steering structures 420, that theymay be centered similar to that discussed above in relation to FIGS. 2a-2 c. As shown, the panel includes substrate 402 with a planar topsurface 404 and interconnect pads 406 aligned in a plurality of rows.Substrate 402 may be a transparent material such as glass, quartz, or aplastic. While FIGS. 4a-4b show only two columns and two rowsincorporating four wells 412, a number of rows (indicated by the smallcase letter following the element identifying numbers (e.g., 420 a,where the “a” indicates the row)) and columns (indicated by the dashnumber following the element identifying numbers (e.g., 440-1, where the“1” indicates the column)) can be used to form a panel.

A first film 410 is disposed over top surface 404 of substrate 402, andwells 412 are defined in first film 410. Each well 412 is aligned in acorresponding row (again, indicated by the small case letter followingthe element identifying numbers) and column (again, indicated by thedash number following the element identifying numbers). Each well 412has a cross-sectional opening 416 that exposes a correspondinginterconnect pad 406. As one particular example, well 412 a-1 exposesinterconnected pad 406 a. In this embodiment, cross-sectional opening416 is depicted as circular, but alternatively it may be square,rectangular, oval, or have a counterbore pocket structure. First film410 may be formed using any process known in the art for forming a layerwith wells. As just one example, first film 410 may be formed using aconformal deposition and selective etching process. Based upon thedisclosure provided herein, one of ordinary skill in the art willrecognize a variety of processes that may be used to form first film 410in accordance with different embodiments. A cross-sectional opening 482of through-hole via 480 is less than cross-sectional opening 416. Insome embodiments, cross-sectional opening 482 is thirty (30) microns.Based upon the disclosure provided herein, one of ordinary skill in theart will appreciate other widths for first through-hole vias 480 inaccordance with different embodiments.

A second film 418 is disposed over first film 410. Second film 418includes plurality of parallel steering structures 420. Each steeringstructure 420 has a width 422 that is greater than cross-sectionalopening 416 of wells 412 and surrounds a number of wells (e.g., steeringstructure 420 a surrounds wells 412 a-1 and 412 a-2; and steeringstructure 420 b surrounds wells 412 b-1 and 412 b-2) such that thesurrounded wells are exposed within the respective steering structure420. In some embodiments, second film 418 is a removable material thatcan be removed prior to deploying the final assembled panel. In otherembodiments, second film 418 is not removed prior to deploying the finalassembled panel. In some embodiments, second film 418 is a differentmaterial than that of first film 410. In other embodiments, second film418 is the same material as that of first film 410. In this embodiment,wells 412 off-center within steering structures 220 such that: a smallportion of the perimeters of wells 412 a-1 and 412 a-2 are coextensivewith a sidewall 490 of second film 418, but a sidewall 491 of secondfilm 418 is not coextensive with any portion of the perimeters of wells412 a-1 and 412 a-2; and a small portion of the perimeters of wells 412b-1 and 412 b-2 are coextensive with a sidewall 492 of second film 418,but a sidewall 493 of second film 418 is not coextensive with anyportion of the perimeters of wells 412 b-1 and 412 b-2. Second film 418may be formed using any process known in the art for forming a layerwith steering structures. As just one example, second film 418 may beformed using a conformal deposition and selective etching process. Basedupon the disclosure provided herein, one of ordinary skill in the artwill recognize a variety of processes that may be used to form secondfilm 418 in accordance with different embodiments.

Diode objects 426 are deposited into wells such that a bottom contact oneach of diode objects are electrically connected to interconnect pads406 exposed by wells 412. A plurality of top electrically conductivetraces 440 are disposed over a column of wells 412 such that anelectrical connection at a top contact 438 of each of the diode objects426 within a given column is made. An insulator material 434 is formedaround each of the diode objects 426 within their respective well 412.As would be known in the art, diode objects 426 may include a lowermaterial with either a p-dopant or an n-dopant and an upper material ofthe opposite dopant type, with an intervening multiple quantum well(MQW). The MQW may be a series of quantum well shells (typically 5layers—e.g., alternating 5 nanometer (nm) of indium gallium nitride(InGaN) with 9 nm of n-doped GaN (n-GaN)). There may also be an aluminumgallium nitride (AlGaN) electron blocking layer between MQW layers andthe p-doped disk. The outer shell may be p-doped GaN (Mg doping) about400 nm thick. A high-brightness blue LED can be formed, or a green LEDif a higher indium content is used in the MQW. The lower material may bea material such as p-GaN, p-doped aluminum gallium indium phosphide(p-AlGaInP), n-GaN, or n-AlGaInP. The upper material may be the same asthe lower material, but oppositely doped. It should be noted that theaforementioned discussion of materials and structure of diode objects426 is not exhaustive, and that one of ordinary skill in the art willrecognize other materials and structures that may be used in relation todifferent embodiments.

In some embodiments, first film 410 has a first thickness 432 and diodeobjects 426 exhibit a similar thickness. In some cases, the differencebetween the thickness of diode object 426 and thickness 432 is less thanfifty (50) percent of the overall thickness of diode object 426.

Turning to FIG. 5, a flow diagram 500 depicts a method in accordancewith one or more embodiments of the present inventions for assemblingdiode objects into a panel. Although the method is depicted as asequence of numbered steps for clarity, the numbering does notnecessarily dictate the order of the steps. It should be understood thatsome of these steps may be skipped, performed in parallel, or performedwithout the requirement of maintaining a strict order of sequence.Following flow diagram 500, a substrate is provided that includes asubstantially planar top surface with interconnect pads aligned in aplurality of rows (block 505). Turning to FIG. 6a , a cross-sectionalview 601 of a portion of a substrate 602 including interconnect pads 606is shown to illustrate the process of block 505 of FIG. 5 with rowsbeing designated “a” and “b”. Bottom trace interconnect (not shown) isalso formed on top of sustrate 602 to connect various of interconnectpads 606.

Returning to FIG. 5, it is determined whether THVs are to be formed inthe substrate (block 510). Where THVs are to be formed (block 510), THVsare patterned and etched in the substrate (block 515). Turning to FIG.6b , a cross-sectional view 603 of a portion of a substrate 602including interconnect pads 606 is shown with THVs 680 extending thoughsubstrate 602 to illustrate the process of block 515 of FIG. 5.Returning to FIG. 5, a first film is formed over the substrate (block520). This may be done using any process known in the art for depositinga material on top of a substrate. Turning to FIG. 6c , a cross-sectionalview 605 of a portion of a substrate 602 having a first film 610 formedthereon is shown to illustrate the process of block 520 of FIG. 5.Returning to FIG. 5, the first film is patterned and etched to formwells exposing interconnect pads 606 and through-hole vias 680 (block525). Turning to FIG. 6d , a cross-sectional view 607 of a portion of asubstrate 602 including wells 612 exposing interconnect pads 606 isshown to illustrate the process of block 525 of FIG. 5. Each well 612has a cross-sectional opening, and is aligned in a corresponding row andcolumn.

Returning to FIG. 5, a second film is formed over the first film (block530). This may be done using any process known in the art for depositinga material on top of a substrate. Turning to FIG. 6e , a cross-sectionalview 609 of a portion of a substrate 602 having a second film 618 formedover first film 610 is shown to illustrate the process of block 530 ofFIG. 5. Returning to FIG. 5, the second film is patterned and etched toform steering structures in relation to wells 612 (block 535). Eachsteering structure has a width greater than the well cross-sectionalopening, and exposes a corresponding column of wells. Turning to FIG. 6f, a cross-sectional view 611 of a portion of a substrate 602 includingsteering structures 620 surrounding a corresponding column of wells 612is shown to illustrate the process of block 535 of FIG. 5. Each well 612has a cross-sectional opening, and is aligned in a corresponding row andcolumn.

Returning to FIG. 5, it is determined whether vacuum pressure is to beemployed in relation to depositing diode objects into the wells (block545). Where vacuum pressure is to be used (block 545), a vacuum pressureis produced under the substrate such that carrier fluid in a suspensionflowing over the surface will be drawn through through-hole vias andtend to cause diode objects suspended in the carrier fluid to be drawninto corresponding wells (block 550). A suspension including the diodeobjects suspended in the carrier fluid is deposited on the surface, andis agitated such that the diode objects deposit into the wells (block555). Where all wells are not yet filled with a diode object (block560), the process of block 555 continues. Otherwise, where all wells arefilled (block 560), the diode objects are connected to the bottom trace,the second film may be removed, an insulator is formed over the diodeobjects and conductive traces formed through the insulator to connectthe diode objects (block 565). Turning to FIG. 6g , a cross-sectionalview 613 of a portion of a substrate 602 including wells 612 filled withdiode object 626 is shown to illustrate the process stage precedingblock 565 of FIG. 5.

In conclusion, the invention provides novel systems, devices, methodsand arrangements for fluidic assembly. While detailed descriptions ofone or more embodiments of the invention have been given above, variousalternatives, modifications, and equivalents will be apparent to thoseskilled in the art without varying from the spirit of the invention. Forexamples, while some embodiments are discussed in relation to displays,it is noted that the embodiments find applicability to devices otherthan displays. As another example, while steering structures are shownas open on the top, in some cases they may be enclosed to make a fluidicflow chamber. Therefore, the above description should not be taken aslimiting the scope of the invention, which is defined by the appendedclaims.

What is claimed is:
 1. A display panel, the display panel comprising: asubstrate with a top surface; a material layer disposed over the topsurface of the substrate, wherein the material layer includes: aplurality of wells, and wherein each of the plurality of wells extendsto a first depth into the material layer; and at least one steeringfeature surrounding two or more of the plurality of wells, wherein thesteering feature extends a second depth into the material layer, andwherein the second depth is less than the first depth.
 2. The panel ofclaim 1, wherein the material layer includes a first sub-layer disposedover the top surface of the substrate and a second sub-layer disposedover the first sub-layer.
 3. The panel of claim 2, wherein a thicknessof the first sub-layer is greater than a thickness of the secondsub-layer layer.
 4. The panel of claim 2, wherein the first depth is athickness of the first sub-layer, and wherein the second depth is athickness of the second sub-layer layer.
 5. The panel of claim 2,wherein the first sub-layer comprises a first material and the secondsub-layer comprises a second material.
 6. The panel of claim 5, whereinthe first material is the same as the second material.
 7. The panel ofclaim 5, wherein the second material is removable.
 8. The panel of claim1, wherein the at least one steering feature is a slot with across-section greater than an opening of each of the two or more of theplurality of wells.
 9. The panel of claim 8, wherein the two or more ofthe plurality of wells is part of a column of wells.
 10. The panel ofclaim 8, wherein the two or more of the plurality of wells each has aperimeter; and wherein the at least one steering feature has a sidewallhaving through-indentations coextensive with at least a portion of theperimeter of each of the two or more of the plurality of wells.
 11. Thepanel of claim 8, wherein the substrate includes interconnect padsaligned in a plurality of rows.
 12. The panel of claim 11, the panelfurther comprising: a light emitting diode (LED) disk situated in eachof the two or more of the plurality of wells, wherein each LED disk hasa cross-sectional width less than a cross-sectional opening of each ofthe two or more of the plurality of wells, and a surface with a firstcontact to make an electrical connection with one of the interconnectpads.
 13. The panel of claim 12, wherein the material layer includes afirst sub-layer disposed over the top surface of the substrate andhaving a first thickness, and a second sub-layer disposed over the firstsub-layer and having a first thickness, and wherein the LED disks haveabout the same thickness as the first thickness.
 14. The panel of claim13, wherein the panel further comprises: an insulator material fillingeach steering feature, with vias exposing a second contact of each ofthe LED disks; and a plurality of top electrically conductive traces,with each top conductive trace connected to the second contact of eachof the LED disks in a corresponding column of wells.
 15. The panel ofclaim 1, wherein the substrate includes a through-hole via (THV)co-located with each of the plurality of wells.
 16. A display panel, thepanel comprising: a substrate with a top surface; a film layer disposedover the top surface of the substrate, wherein the film layer includes aplurality of wells extending into the film layer and exposing the topsurface of the substrate; and a steering structure disposed over thefilm layer, wherein the steering structure surrounds two or more of theplurality of wells.
 17. The panel of claim 16, wherein the steeringfeature is a slot with a cross-section greater than an opening of eachof the two or more of the plurality of wells.
 18. The panel of claim 16,wherein the two or more of the plurality of wells is part of a column ofwells.
 19. The panel of claim 16, wherein the two or more of theplurality of wells each have a perimeter; and wherein the steeringstructure has a sidewall having through-indentations coextensive with atleast a portion of the perimeter of each of the two or more of theplurality of wells.
 20. The panel of claim 16, wherein the substrateincludes interconnect pads aligned in a plurality of rows.
 21. The panelof claim 20, the panel further comprising: a light emitting diode (LED)disk situated in each of the two or more of the plurality of wells,wherein each LED disk has a cross-sectional width less than across-sectional opening of each of the two or more of the plurality ofwells, and a bottom surface with a lower contact to make an electricalconnection with one of the interconnect pads.
 22. The panel of claim 16,wherein the substrate includes a through-hole via (THV) co-located witheach of the plurality of wells.
 23. A display panel, the display panelcomprising: a substrate with a planar surface; a film layer disposedover the planar surface of the substrate, wherein the film layerincludes a plurality of wells extending a first depth into the filmlayer; and a steering structure disposed over the film layer andextending a second depth from the film layer, wherein the steeringstructure surrounds two or more of the plurality of wells.
 24. The panelof claim 23, wherein the steering feature is a slot with a cross-sectiongreater than an opening of each of the two or more of the plurality ofwells.